1. Field of the Invention
The present invention relates to flexible heaters, and more particularly to a novel flexible heater adapted to be hand-held as a warmer or be insertably received in gloves, boots or other wearing apparel for the purpose of heating a specified area and which will readily flex during movement of the person wearing the heater so that conductive circuits will not be broken or disrupted. The heater further incorporates a plurality of resistive components composed of selective ohmic values.
2. Brief Description of the Prior Art
In the past, it has been the conventional practice to provide a variety of heaters which employ wires that are directly embedded in various portions of clothing so that the wearer of the clothing will receive the benefit of heat. This has been particularly useful in the aviation industry where wires have been run through flying clothing as well as flying boots wherein the principles of electrical resistive heating are used. However, problems and difficulties have been encountered when employing such clothing with wire conductive paths that stem largely from the fact that wires readily break when flexed so that body movements of the wearer tend to sever electrical conductive paths disrupting the circuits. In such instances, the use of the device as a heater is completely eliminated and rendered useless for its intended purpose.
Attempts have been made to overcome the above problems and difficulties by employing electrical circuit design and materials which are flexible and pliable and are not subject to structural fatigue. Such a flexible heater is disclosed in U.S. Pat. No. 4,948,951. However, conductive strips are disclosed which are made by means of a substrative method through a chemical etching process which removes material and which are of a fixed resistance with no means for resistive adjustment. The prior structures are not suitable for being layered which is an additive construction and provides a selective means for adjusting or establishing desired values of resistance.
Therefore, a need has existed to provide a flexible unitary structure of conductive strips arranged in an overlapping relationship so that selective intersection may be joined to establish resistances of desired values. In this manner, a flexible heater is envisioned which creates a uniform heater that may be "screened on" to an insulative substrate or base layer in an "additive" or layered construction rather than in a "substractive" construction such as chemical etching.